#include "gcpch.h"
#include "hsieh_hashfn.h"

#ifdef get16bits
#   undef get16bits
#endif

#define get16bits(d) (*((const uint16_t *) (d)))

typedef unsigned int uint32_t;
typedef unsigned short uint16_t;

unsigned int geek_hsieh_hashfn(const char *data, int len)
{
    uint32_t hash = len, tmp;
    int rem;

    if (len <= 0 || data == NULL) return 0;

    rem = len & 3;
    len >>= 2;

    /* Main loop */
    for (;len > 0; len--)
    {
        hash  += get16bits (data);
        tmp    = (get16bits (data+2) << 11) ^ hash;
        hash   = (hash << 16) ^ tmp;
        data  += 2*sizeof (uint16_t);
        hash  += hash >> 11;
    }

    /* Handle end cases */
    switch (rem)
    {
        case 3: hash += get16bits (data);
            hash ^= hash << 16;
            hash ^= data[sizeof (uint16_t)] << 18;
            hash += hash >> 11;
            break;
        case 2: hash += get16bits (data);
            hash ^= hash << 11;
            hash += hash >> 17;
            break;
        case 1: hash += *data;
            hash ^= hash << 10;
            hash += hash >> 1;
    }

    /* Force "avalanching" of final 127 bits */
    hash ^= hash << 3;
    hash += hash >> 5;
    hash ^= hash << 4;
    hash += hash >> 17;
    hash ^= hash << 25;
    hash += hash >> 6;

    return hash;
}
